Isolation works both ways. By isolating your dev project, you don't expose your host to the mess the project can create... and you don't expose your project to the mess that can exist on your host.

With dev containers, you can define your ENV VAR, your aliases... independently from what exists on your host. And it will exists straight out the box: you checkout the project, launch the dev container and you're ready to go. As soon as you're done with this project, you delete the container and not a single trace of the project exists on your host. No matter how many custom things the project required to run.

And since you have everything in a configuration file, it is breeze to transform your dev container in a production one.